In the field of endo-photocoagulation laser treatment at the retina during eye surgery, it is desirable to reduce the size of the entry site in order to have less trauma and recovery time for the patient.
Most often, and as in other fields is medical surgery, a trocar system is used, whereby a cannula is inserted at the entry site with the assistance of a puncturing device/instrument. Once the cannula is in place, the puncturing device/instrument is withdrawn and the cannula serves as an opening that allows one or more device to enter through the cannula and into the surgical site where it is needed.
As the industry has moved toward smaller diameters (typically, 27 gauge, 25 gauge, and 23 gauge, as opposed to the larger, 20 gauge), such current systems prove to have engineering limitations, as the small gauge instruments tend to flex at the entry point when the direction of the instrument (generally via a hand held instrument base) is changed in order to target other areas in the general proximity.
As the outside diameter of the cannula is always larger than the outside diameter of the device to be inserted therethrough, it is important to note that a 25 gauge instrument will use close to 23.5 gauge cannula, and a 23 gauge instrument will use close to 21.5 gauge cannula.
In practice, with the 23 gauge system, the entry wound diameter is reduced by about 15%, and for the 25 gauge system, it is reduced by about 33%, in comparison with the 20 gauge system.
With the 25 gauge system, the flexibility of the instruments reached an upper limit that not all surgeons are comfortable with, opting instead for the larger 23 gauge system.
As for the 27 gauge system, the flexibility is reduced by using a reinforcing sleeve that stays close to the cannula entry, using the physics of a cantilever, where rigidity is the strongest at the base (or lateral movement is the lowest) compared to the distal end, as in the case of U.S. patent application Ser. No. 11/268,928.
Such size and technique provides very little control over changing the direction of the instrument and is used only in very simple operation where the target area is very small.
Hence, a new approach is needed in order to use smaller gauge instruments, increasing the level of manipulation by the surgeon, with the least amount of sacrifice in performance.